1. Field of the Invention
This invention relates to a method of manufacturing a granulated body for absorbing excrement of animals, in which wood fibers and dry bamboo fibers are used for granulation as a chief material or dry bamboo fibers are used for granulation as a chief material and a water absorbing property is provided thereto.
2. Related Art
As shown in patent documents 1 and 2, a granulated body for excrement of animals in which a plurality of granulated bodies obtained by granulating wood fibers and providing a water absorbing property thereto are laid in a tray receptacle and subjected to excrement of pet animals such as cats, experimental animals or the like.
The patent document 1 shows granulated bodies obtained by using wood fibers as a chief material and selectively mixing inorganic filler, starch, water-absorptive polymer and the like. In order to obtain those granulated materials, a method is employed in which the main material and the mixing material are admixed in a hydraulic state, the resultant is cut and granulated at an outlet port side while extruding the resultant by an extruder. That is, the admixed main material and mixing material, which are in a wet state by water applied thereto, are extrusion molded so as to be granulated. After being granulated, they are dried to form a porous structure which is required for absorbing excrement.
Also, another method is employed for granulation, in which the main material and the mixing material are admixed in a hydraulic state, and the resultant is rollingly moved on an inner peripheral surface of a rotating cylinder. That is, as in the case with the extrusion molding, the wet admixed materials are roll-molded so as to be granulated. After being granulated, they are dried to form a porous structure which is required for absorbing excrement.
On the other hand, the patent document 2 shows a method, in which the admixed material of the main material and the mixing material is compression molded in a non-hydraulic state and granulated such that they each have a fixed shape.
[Patent Document 1]
Official Gazette of Japanese Patent Application Laid-Open No. H08-182437
[Patent Document 2]
Official Gazette of Japanese Patent Application Laid-Open No. H10-113087
However, the method for providing a porous structure of a granulated body shown in the patent document 1 has the following problems. The porous structure of the granulated body formed in accordance with the teaching of the patent document 1 depends on the degree of transpiration of water by drying. Therefore, it is difficult for this method to obtain a sufficient degree of porosity and porosity ratio. Moreover, the wood fibers are inferior in water absorption due to their fibrous structure and formation of the porosity by transpiration of moisture existing among the fibers is limited.
In addition, in the case of water sensitive coagulants as represented by starch and PVA, which exhibit a viscous property and a water retaining property when they detect moisture, are admixed in order to prevent excessive collapsion when the granulated body absorbs excrement and swells, those water sensitive coagulants are deteriorated upon absorption of moisture to degrade the viscous property during use.
On the other hand, the granulated body granulated by hydraulic compression molding as shown in the patent document 2 can prevent deterioration in efficiency of the water sensitive coagulant. However, the degree of porosity and porosity ratio are badly reduced by hard clamping made by a closed mold, and the water absorbing efficiency for absorbing water from excrement is lowered during use. That is, it lacks capability for absorbing water and capturing excrement at the same time it contacts the excrement. In other words, it lacks speed of water absorption and allows excrement to spread widely.